Vapor phase transport of AlN in an RF heated reactor: Low and high temperature studies
- PDF / 258,173 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 39 Downloads / 134 Views
Y2.8.1
Vapor phase transport of AlN in an RF heated reactor: Low and high temperature studies V. Noveskia,b, R. Schlessera, J. Freitasc. Jr, S. Mahajanb, S. Beaudoind, Z. Sitara a
Department of Materials Science and Engineering North Carolina State University, Raleigh, NC, 27695-7919, USA b Department of Chemical and Materials Engineering Arizona State University, Tempe, AZ, 85287-6006, USA c Naval Research Laboratory, Washington DC, USA d School of Chemical Engineering Purdue University, West Lafayette, IN, 47907-2100, USA
ABSTRACT AlN crystals were grown from the vapor phase in an RF heated AlN sublimation reactor. The studies were performed with the following goals: 1) to optimize the growth rate by investigating mass transfer effects, and 2) to establish a process for epitaxial growth on AlN seeds. A one-dimensional mass transfer model based on equilibrium sublimation and gas-phase diffusion was developed. Model parameters were estimated and the model was validated from growth experiments carried out in a 600 Torr nitrogen atmosphere and temperatures ranging from 2000 to 2400°C. Continuous growth on AlN seed crystals was accomplished as a result of optimizing the initial stage of growth and achieving a delicate balance between the rate of mass transfer and the rate of surface rearrangement. During this experimental study, centimeter-size single crystals of AlN were obtained within the 1.25” diameter boule that was grown at a predicted growth rate of 0.1-0.3 mm/hr, at 500 Torr of nitrogen, short source-to-seed distance, low supersaturation and growth temperatures of 2110-2140°C. Chemical analysis of impurities in the grown AlN boules confirmed a very low oxygen contamination of 100 ppm wt. Cathodoluminescence studies showed well defined near band edge emission peak located slightly above 6 eV. INTRODUCTION III-N thin films grown on classical substrates (SiC or Al2O3) by epitaxial growth techniques typically have large density of extended defect, mainly dislocations (1010 cm-2) [1,2], which affect device performance and lifetime. The dislocation density has been successfully reduced by a few orders of magnitude (down to106-107 cm-2) using alternative methods, such as epitaxial lateral overgrowth (ELO) and hydride vapor phase epitaxy (HVPE) [3]. However, a further reduction of dislocations is needed to optimize device performance. The use of native substrates is expected to decrease dislocation density below 1000 cm-2. Therefore, the growth of bulk AlN and GaN crystals for wafer fabrication is anticipated to have an impact on all III-N based devices. One of the most promising techniques for growth of AlN bulk crystals is the sandwich sublimation method [4-8]. Oxygen is a very common impurity in AlN crystals. It has a significant influence on the electrical and optical properties of the material acting as a deep donor and leading to broad absorption bands in the range of 3.5 to 5.5 eV [9]. A low oxygen contamination is highly desired
Y2.8.2
for high performance of AlN based optoelectronic and electronic device
Data Loading...
